ver acquired by these devoted public servants in attendance
upon cases of that fever. Henceforth they will make use of sulphur or
sulphurous ointment to keep the little infection-carriers at a
distance, and not one medical man or nurse will catch the disease,
still less be killed by it.

A remarkable fact in this history is that the actual parasitic germ
which causes typhus, whether a bacterium (Schizophyte) or a protozoon,
has not been detected, although the louse has been shown to be its
"carrier." The same is true of yellow-fever: we have not seen with the
microscope the microbe which produces it. But we know with certainty
that the gnat, _Stegomya fasciata_, and no other, is the carrier of
the unseen germ, and that we can obliterate that fever by obliterating
the gnat. So, too, although we know how the infection of rabies acts,
and how it is carried, yet no one has yet isolated and recognised the
terrible infective particle itself. There is a very high probability
that in these cases, and also in cancer (where as yet no specific
infective germ or parasitic microbe has been detected), such an
infective microbe is nevertheless present, and has hitherto escaped
observation with the microscope on account of its excessive minuteness
and transparency.

CHAPTER XXI

CARRIERS OF DISEASE

It has now been discovered that a great number of human diseases are
caused by microscopic parasites, which are spoken of in a general way
by the name invented by the great Pasteur, viz. "microbes."
Wool-sorter's disease, Eastern relapsing fever, lock-jaw, glanders,
leprosy, phthisis, diphtheria, cholera, Oriental plague, typhoid
fever, Malta fever, septic poisoning and gangrene have been shown to
be caused each by a peculiar species of the excessively minute
parasitic vegetables known as bacteria (or Schizophyta). Others, for
example, malaria and sleeping sickness, have been shown to be caused
by almost equally minute microbes, which are of an animal nature, and
similar to the free-living animalcules which we call Protozoa, or
"simplest animals," whilst a third lot of diseases--rabies, smallpox,
yellow fever, scarlet fever, and typhus--are held to be caused by
similar minute parasites, although these have not yet actually been
seen and cultivated, but are surely inferred (from the nature and
spread of these diseases) to exist.

The difference of the microbes called bacteria from the
disease-causing microbes classed as "Proto